This invention is concerned with laser diodes, and more specifically with the efficient generation of two opposed and substantially co-linear beams from a single laser diode, as well as three intersecting beams from a single laser diode. The invention is also concerned with such beam generation in a self-leveling laser instrument of the type disclosed in application Ser. No. 248,517 referenced above, and that disclosure is incorporated herein by reference (now U.S. Pat. No. 5,459,932).
Compact battery-operated laser projectors are used in the construction industry for alignment purposes. The visible beam of light projects a straight line in space which can be used to locate building references. A leveled or plumb beam of light can be used to set the level or plumb directions of building elements such as floors, walls and columns. In many applications a small-diameter visible laser beam replaces a string line. The beam strikes an object producing a small spot of light. The center of the spot may be marked with a pencil as needed. Two co-linear beams are often desired to produce two spots of light which are the end points of a straight line; two or three intersecting beams are often needed for other applications. In a typical application replacing a plumb bob, a spot of light on the floor is located directly below a spot on the ceiling. For example, in U.S. Pat. No. 5,144,487 two co-linear beams are generated using a beam splitter and a mirror, as are three intersecting beams.
In construction alignment it is desirable to have two intersecting laser beams at 90.degree. to each other or in some cases to have three intersecting beams at 90.degree. to each other. In a typical application, one of the three beams can be used as a plumb reference up or down while the other two beams are level reference beams. In U.S. Pat. No. 5,144,487, referenced above, multiple beams are produced using beam splitters which do not satisfy the intersection condition. An offset between the horizontal and vertical beams results which is a handicap to the user. In addition, the method for generating multiple intersecting beams is less efficient than that of the present invention.
Other methods of using a beam splitter and subsequent mirrors and glass plates are straightforward but cumbersome. The present invention offers a more compact and efficient design which has lower manufacturing cost.